Packaged pressure sensor device

ABSTRACT

Embodiments of a packaged electronic device and method of fabricating such a device are provided, where the packaged electronic device includes: a pressure sensor die having a diaphragm on a front side; an encapsulant material that encapsulates the pressure sensor die, wherein the front side of the pressure sensor die is exposed at a first major surface of the encapsulant material; an interconnect structure formed over the front side of the pressure sensor die and the first major surface of the encapsulant material, wherein an opening through the interconnect structure is generally aligned to the diaphragm; and a cap attached to an outer dielectric layer of the interconnect structure, the cap having a vent hole generally aligned with the opening through the interconnect structure.

BACKGROUND Field

This disclosure relates generally to packaged devices, and morespecifically, to packaged pressure sensor devices.

Related Art

Pressure sensors are utilized in a variety of applications, such as in atire pressure monitoring system (TPMS) for a vehicle. TPMS pressuresensors may be packaged with a radio frequency transmitter that isconfigured to transmit real-time tire pressure information from thepressure sensor to a main TPMS control unit, which in turn provides anindication (e.g., a warning) to a driver of the vehicle regarding thetire pressure information.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1-6 illustrate cross-sectional views depicting various steps of aprocess for fabricating an example packaged pressure sensor device,according to some embodiments of the present disclosure.

FIG. 7 illustrates a cross-sectional view of an example packagedpressure sensor device attached to a printed circuit board (PCB),according to some embodiments of the present disclosure.

FIG. 8 illustrates a perspective view of an example layout of componentsincluded in the packaged pressure sensor device, according to someembodiments of the present disclosure.

FIGS. 9 and 10 illustrate perspective views of an example packagedpressure sensor device, according to some embodiments of the presentdisclosure.

The present invention is illustrated by way of example and is notlimited by the accompanying figures, in which like references indicatesimilar elements, unless otherwise noted. Elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale.

DETAILED DESCRIPTION

The following sets forth a detailed description of various embodimentsintended to be illustrative of the invention and should not be taken tobe limiting.

Overview

Conventional packaged pressure sensor devices may be implemented using asubstrate or lead frame like a QFN (quad flat no-lead), where componentsare interconnected by wire bond. Such a device may require a largeclearance for the wire bonds, which may be greater than 1 mm in someexamples, resulting in a large X and Y profile package having a totalheight of over 2 mm. Further, a housing may be formed around the wirebonds and the pressure sensor on the QFN, which may be filled with gelto protect the pressure sensor. The housing may include a center venthole to allow pressure from the surrounding environment to reach thepressure sensor through the gel. However, such an arrangement includesthe risk of wire bond sagging. Further, the pressure sensor is separatedfrom the surrounding environment by a large distance (e.g., the distancefrom the pressure sensor to the vent hole may be greater than 1 mm), anda large amount of gel may be required to fill the housing.

Embodiments of the present disclosure provided herein include a packagedpressure sensor device and method of making that uses a redistributionlayer (RDL) structure (also referred to as an interconnect structure) toavoid the use of wire bonds and eliminates the risk of wire bondsagging. The RDL structure is formed over the front side of a pressuresensor die (or cell) and another electronic component, such as anintegrated circuit (IC) component that implements a radio frequency (RF)transmitter, signal processing circuitry, or both. In some embodiments,the RDL structure has a height in a range of approximately 0.01 mm to0.05 mm, which provides interconnects or signal paths between componentsof the packaged pressure sensor device that are much shorter thansimilar interconnects formed by looping wire bonds, resulting in afaster response time. An opening is formed through the RDL structure,which is generally aligned with a diaphragm on the front side of thepressure sensor die or cell. The opening is filled with gel to protectthe diaphragm of the pressure sensor die. Since the opening through theRDL structure requires a much smaller volume of gel (as compared with amuch larger volume under the housing), cost of the packaged pressuresensor device may be reduced. A cap may be placed over the RDLstructure, with a vent hole generally aligned with the diaphragm,forming a front major surface for pressure sensing. In this manner, thedistance between the pressure sensor and the vent hole is greatlyreduced (e.g., a distance equivalent to the thickness of the RDLstructure, which is may be smaller than the 1 mm clearance required forlooping wire bonds). The packaged pressure sensor device also includesbackside external connections (which may include solder balls) locatedon a back major surface of the packaged pressure sensor device that isopposite the front major surface. Such an arrangement prevents anystress introduced by the solder balls attached to the externalconnections from interfering with operation of the pressure sensor. Insome embodiments, a total height of the resulting packaged pressuresensor device is approximately 1 mm, resulting in a lower profiledevice.

Example Embodiments

FIG. 1-6 show cross-sectional views of various steps performed on adevice structure 100 to fabricate a packaged pressure sensor device. Thecross-sectional views of device structure 100 are representative of thecomponents included in the device structure 100, which may have acomponent layout that differs from that shown in FIG. 1-6 (e.g., seeFIG. 8). In some embodiments, the device structure 100 is implemented ina 9 mm by 9 mm footprint, which may be differently sized in otherembodiments. The single device structure 100 shown in FIG. 1-6 may berepresentative of a number of device structures formed as part of anarray or reconstituted wafer of device structures 100 that are thensingulated into a plurality of packaged devices, where the various stepsdiscussed herein are implemented on all device structures of the array.

In FIG. 1, device structure 100 includes a number of components attachedto a temporary carrier 105 by an adhesive tape 110. In the embodimentshown, such components include a pressure sensor die or cell (P-cell)115, an integrated circuit (IC) component 130, a gyroscope sensor die orcell (G-cell) 135, and a signal connection structure 140, althoughadditional or fewer components may be included in other embodiments. Forexample, a separate power source such as a battery (not shown) may alsobe included in device structure 100 to power the resulting packagedpressure sensor device in some embodiments, while the G-cell 135 may beabsent in other embodiments.

P-cell 115, IC component 130, and G-cell 135 each have a back side 160and a front side 165, with one or more pads 125 formed on the front side165. P-cell 115, IC component 130, and G-cell 135 has its front side 165attached to a temporary carrier 105 by tape 110 (e.g., die 115, 130, and135 are attached in a face-down orientation). In some embodiments,temporary carrier 105 is formed from a polymer film such as ceramic,glass, or similar materials, where a double-sided tape 110 is placed ona surface of the polymer film. In some embodiments, the tape 110 isformed from a polymer film, such as PVC (polyvinyl chloride),polyolefin, polyethylene, or similar material, and is removable inresponse to UV (ultraviolet light) exposure or temperature excursion(e.g., the tape 110 weakens in response to the UV exposure ortemperature excursion). In some embodiments, temporary carrier 105includes a release layer to release the wafer from the tape 110.

P-cell 115 implements a pressure sensor (e.g., a MEMS(microelectromechanical structure) device) configured to measurepressure in an environment. P-cell 115 includes a diaphragm 120 on thefront side 165 as part of the pressure sensor. In some embodiments, thepressure sensor is implemented as a capacitive transducer, where thediaphragm 120 acts as one plate of a capacitive element. The capacitivevalue of the capacitive element changes with pressure-induceddisplacement of the diaphragm 120, where the pressure sensor convertsthe capacitive value into a pressure measurement signal. In otherembodiments, the pressure sensor is implemented as a piezo-resistivetransducer, where the diaphragm 120 implements piezo-resistive elements,which may be diffused into or bonded to the diaphragm 120. The resistivevalue of the piezo-resistive elements changes with pressure-inducedstrain on the diaphragm 120, where the pressure sensor converts theresistive value into a pressure measurement signal.

IC component 130 includes active circuitry that implements signalprocessing circuitry configured to receive the pressure measurementsignal from P-cell 115 (through an interconnect structure 525 furtherdiscussed in connection with FIG. 5) and calibrate or correct thepressure measurement signal in order to output accurate pressurereadings. For example, the signal processing circuitry may includelinearization circuitry to improve linearity in the pressure measurementsignal. In some embodiments, the signal processing circuitry of ICcomponent 130 may further include temperature correction circuitryconfigured to adjust or correct the pressure measurement signal based ona temperature reading from a temperature sensor (not shown) that isimplemented in the device structure 100 in some embodiments (e.g.,pressure is temperature-dependent). In some embodiments, the signalprocessing circuitry may implement additional circuitry (e.g., a signalamplifier or a signal monitor) that has configurable settings (e.g.,configurable gain or configurable monitoring thresholds) to furtheradjust the pressure measurement signal to output accurate pressurereadings.

IC component 130 also includes a radio frequency (RF) block thatimplements an RF transmitter and antenna configured to transmit sensordata, including pressure readings, to a main control unit. For example,the IC component 130 and the main control unit may be implemented in atire pressure monitoring system (TPMS) for a vehicle, where P-cell 115is used to monitor tire pressure of a given tire on the vehicle. Thesensor data received by the TPMS main control unit may be used by avehicle control system, such as a driver assistance system, to provideinformation or warnings to the driver (e.g., low tire pressure warning).In some embodiments, the sensor data transmitted to the main controlunit also includes temperature readings. In some embodiments, sensordata may also include a unique identifier or serial number of the P-cell115.

In some embodiments, the RF block of IC component 130 also implements anRF receiver, providing transceiver functionality for bidirectionalcommunication between the RF block and the main control unit. The RFblock of IC component 130 implements front end components of the RFtransmitter, RF receiver, or both, where the front end components mayinclude but are not limited to a transmitter power amplifier, a receiverlow noise amplifier, one or more baluns, one or more filters, acirculator or other coupling device to the antenna, impedance matchingelements, an oscillator, a phase locked loop, and other appropriatefront end elements. The front end components of the RF block (e.g., anamplifier) may have configurable settings (e.g., configurable gainsetting) to adjust the output signal that conveys the sensor data. Insome embodiments, the RF block may have an operating frequency thatfalls within a frequency band of 300 to 500 MHz, although otheroperating frequencies that fall within other radio frequencies may beimplemented in other embodiments.

In some embodiments, IC component 130 also implements control logicconfigured to control the signal processing circuitry and the RF block.For example, control logic may adjust the configurable settings of thesignal processing circuitry, the RF block, or both to achieve accuratepressure readings that are provided to the main RF receiver. Inembodiments where the RF block implements an RF receiver, the controllogic may receive information from the main control unit that is used tocontrol the configurable settings of the signal processing circuitry, RFblock, or both.

In some embodiments, IC component 130 implements a microcontroller thatincludes one or more of the signal processing circuitry, the controllogic, and the RF block. In some embodiments, one or more of the signalprocessing circuitry, the control logic, and the RF block may beimplemented as separate components in the device structure 100. In someembodiments, IC component 130 may further include a power source (e.g.,a battery) to power the resulting packaged pressure sensor device.

G-cell 135 implements a gyroscope (e.g., a MEMS (microelectromechanicalstructure) device) or similar sensor for sensing movement. For example,G-cell 135 may be implemented in the TPMS for a vehicle and isconfigured to sense whether the vehicle is at rest or in motion. G-cell135 outputs a velocity measurement that is conveyed to IC component 130(through an interconnect structure 525 further discussed in connectionwith FIG. 5). IC component 130 may be configured to transmit sensor datato the main control unit when the vehicle is in motion, and mayotherwise be in an idle or standby mode (that does not transmit sensordata) when the vehicle is at rest (e.g., when the tires are not spinningor have zero velocity).

Signal connection structure 140 includes a dielectric material in whicha number of conductive conduits or vias 145 are embedded. Conductiveconduits 145 are formed from a conductive material that extends throughthe dielectric material of signal connection structure 140. Examples ofthe conductive material include but are not limited to copper, aluminum,silver, gold, an alloy or composite of one or more suitable conductivemetals, and the like. The conductive conduits 145 are each exposed at abottom surface 165 of the signal connection structure 140, which isattached to temporary carrier 105 by tape 110. The conductive conduits145 each have a ball attach pad 150 that is exposed at a top surface 160of the signal connection structure 140, with a solder ball 155respectively attached to each of the ball attach pads 150. Someembodiments may not include solder balls 155. In the embodiment shown,signal connection structure 140 is located around the periphery or edgeof the device structure 100 and surrounds P-cell 115, IC component 130,and G-cell 135, but may be differently located or differently shaped inother embodiments.

The active circuitry and sensor die or cells described herein can beimplemented on a semiconductor substrate or wafer, which can be anysemiconductor material or combinations of materials, such as galliumarsenide, silicon germanium, silicon-on-insulator (SOI), silicon,monocrystalline silicon, the like, and combinations of the above. Theactive circuitry is formed using a sequence of numerous process stepsapplied to the semiconductor wafer, including but not limited todepositing semiconductor materials including dielectric materials andmetals, such as growing, oxidizing, sputtering, and conformaldepositing, etching semiconductor materials, such as using a wet etchantor a dry etchant, planarizing semiconductor materials, such asperforming chemical mechanical polishing or planarization, performingphotolithography for patterning, including depositing and removingphotolithography masks or other photoresist materials, ion implantation,annealing, and the like. Examples of components implemented in theactive circuitry include but are not limited to a processor, memory,logic, analog circuitry, sensor, MEMS (microelectromechanical systems)device, a standalone discrete device such as a resistor, inductor,capacitor, diode, power transistor, and the like. In some embodiments,the active circuitry may be a combination of the components listed aboveor may be another type of microelectronic device. The wafer is thensingulated into a number of sensor die or cells or active circuitrycomponents, which may be then implemented in the device structure 100.

FIG. 2 shows the device structure 100 after overmolding. P-cell 115, ICcomponent 130, G-cell 135, and signal connection structure 140 areencapsulated with an encapsulant material such as mold compound 205,which covers the back sides 160 and side walls of P-cell 115, ICcomponent 130, and G-cell 135. In some embodiments, mold compound 205may be a biphenyl type or multi-aromatic type epoxy resin, but may beother types of encapsulating materials in other embodiments. Theovermolding may be performed by an encapsulating method, such astransfer molding or other types of other encapsulating methods. In someembodiments, overmolding results in a reconstituted wafer of a pluralityof device structures encapsulated in the mold compound 205, where thereconstituted wafer has a front side still attached to temporary carrier105 by tape 110.

FIG. 3 shows the device structure 100 after grinding. A portion of themold compound 205 is removed by a grinding step, such as chemicalmechanical polishing (CMP), to reveal a new back surface (or majorsurface) 305 of the mold compound 205. The remaining portion of the moldcompound 205 continues to cover and embed back sides 160 and side wallsof P-cell 115, IC component 130, and G-cell 135. In some embodiments,the grinding is performed on a back side of the reconstituted wafer.Surfaces 310 of the solder balls 155 are also exposed in the backsurface 305 to provide backside external connections for the resultingpackaged pressure sensor device, as further discussed below.

FIG. 4 shows the device structure 100 after the temporary carrier 105and tape 110 have been removed, which shows front sides 165 of P-cell115, IC component 130, G-cell 135, and signal connection structure 140exposed through a front surface (or major surface) 405 of the moldcompound 205. The conductive conduits 145 each have a surface 410exposed at the front side 165 of signal connection structure 140, whichis also referred to as being exposed at the front surface 405 of themold compound 205. The device structure 100 (or thinned reconstitutedwafer) has a resulting thickness or height 415 that is approximately0.65 mm in some embodiments.

FIG. 5 shows the device structure 100 after an interconnect structure525 has been formed over the front sides 165 of P-cell 115, IC component130, G-cell 135, and signal connection structure 140 and major surface405 of mold compound 205. Interconnect structure 525 includes a numberof dielectric layers and conductive layers to form interconnects thatcommunicatively couple P-cell 115, IC component 130, G-cell 135, andsignal connection structure 140. In some embodiments, interconnectstructure 525 implements a fan-out wafer level packaging (FOWLP)arrangement to connect pads 125 of P-cell 115, IC component 130, G-cell135 to surfaces 410 of the conductive conduits 145 of signal connectionstructure 140 arranged around the periphery or edge of the devicestructure 100. In some embodiments, the interconnect structure 525 isformed by a photolithography process. The photolithography process mayinclude depositing a first dielectric layer 505 over (e.g., directly on)the front sides 165 of P-cell 115, IC component 130, G-cell 135, andsignal connection structure 140, and over (e.g., directly on) the majorsurface 405 of mold compound 205. Dielectric layer 505 is a layer ofinsulating material that may be conformally deposited in someembodiments, or spun-on in other embodiments. In some embodiments, theinsulating material used to form interconnect structure 140 includes apositive or negative photo resist material. It is preferred that a softphoto resist material is used, which serves to protect the diaphragm 120from damage during formation of the interconnect structure 525.

Dielectric layer 505 is patterned, developed, and etched to form anumber of openings or via holes 510 through dielectric layer 505 toexpose pads 125. A conductive layer 515 is deposited over the dielectriclayer 505 and into openings 510, which are then patterned to form theinterconnects. Conductive layer 515 is a conductive material that may beconformally deposited, sputtered, printed, or otherwise applied.Examples of the conductive material include but are not limited tocopper, aluminum, silver, gold, an alloy or composite of one or moresuitable conductive metals, and the like. Another dielectric layer 520(of the insulating material) is then deposited over the interconnects,providing an outer surface 535 of the interconnect structure 525. Thedescribed steps may be repeated to form additional layers ofinterconnects in the interconnect structure 525, with a last dielectriclayer providing the outer surface 535. The interconnects of interconnectstructure 525 provide redistributed routing that eliminates the need forwire bonds and allows for the assembly of a low profile pressure sensorpackage.

An opening 530 that is generally aligned to diaphragm 120 is also formedthrough the interconnect structure 525. The opening 530 may be formed bypatterning, developing, and etching the dielectric layers (of theinsulating material) of the interconnect structure 525, which exposesdiaphragm 120 in the opening 530. In the embodiment shown, the opening530 has sloped side walls with a narrowest portion of the opening 530closest to the front side 165 of the p-cell 115, although the opening530 may be differently shaped in other embodiments (e.g., parallelvertical side walls). In some embodiments, the narrowest portion of theopening 530 is wider than the diaphragm 120 (e.g., a perimeter of theopening 530 surrounds a perimeter of the diaphragm 120) to ensure thatthe opening fully surrounds and exposes the diaphragm 120. It is notedthat “generally aligned” indicates that the opening 530 is formed overdiaphragm 120 such that diaphragm 120 is fully exposed within opening530, where the diaphragm 120 may be centered within the opening 530 oroff-centered within the opening 530. For example, in the embodimentshown, the diaphragm 120 is off-centered within opening 530, which maybe due to any minor imperfections or deviations, if any, that arise fromusual and expected process abnormalities that may occur duringfabrication of the interconnect structure 525, which fall withinexpected tolerances.

FIG. 6 shows the device structure 100 after a gel material 605 isdeposited within opening 530. In some embodiments, gel 605 is a lowmodulus and low viscosity material (e.g., a low viscosity siliconepotting gel). The gel material 605 protects the diaphragm 120 fromdamage during and after the fabrication process, while also allowingpressure to be conveyed through gel 605 and sensed by diaphragm 120. Thegel material 605 may be applied by dispensing, printing or spin coating,which is then cured (e.g., by heat or ultraviolet light radiation). Inthe embodiment shown, the gel material 605 fills substantially theentire opening 530, although the gel material 605 may fill less than theentire opening 530 in other embodiments.

FIG. 6 also shows the device structure 100 after a cap 610 is attachedto an outer surface 535 of the last dielectric layer of the interconnectstructure 525. Cap 610 includes a vent hole 615 (or cavity that extendsthrough cap 610) that is generally aligned with the diaphragm 120 overopening 530, where the vent hole 615 is not required to be centered inthe cap 610. In the embodiment shown, vent hole 615 is narrower thanopening 530, which protects the gel 605 and the diaphragm 120 of p-cell115 from damage (e.g., debris in the environment), while still allowingpressure from the environment to be sensed by diaphragm 120. In theembodiments shown, the diaphragm 120 is separated from the vent hole 615by the height 620 of the interconnect structure 525, which minimizes thedistance between diaphragm 120 and the surrounding environment,providing a more direct measurement of pressure in the environment. Insome embodiments, the vent hole 615 is smaller than a widest portion ofthe opening 530 (e.g., a perimeter of the opening 530 surrounds aperimeter of the vent hole 615). It is noted that “generally aligned”also indicates that the vent hole 615 is located over opening 530 suchthat a portion of the opening 530 is exposed within the vent hole 615,where the vent hole 615 may be centered over the opening 530, may becentered over the diaphragm 120, or may be positioned elsewhere over theopening 530, where in each case the diaphragm 120 may be centered oroff-centered within the opening 530.

In some embodiments, cap 610 (with the exception of the portion of cap610 that overlies opening 530) makes direct contact with the entiremajor surface 535 of the last dielectric layer of the interconnectstructure 525, which also protects the interconnect structure 525 fromdamage (e.g., debris in the environment). An outer surface 630 of cap610 may be referred to as a front major surface of the resultingpackaged pressure sensor device that provides pressure sensing, andouter surface 305 may be referred to as a back major surface of theresulting packaged pressure sensor device that provides externalconnections (also referred to as backside external connections), such asto a printed circuit board (PCB) shown in FIG. 7.

In some embodiments, cap 610 is a metal cap that is attached by adhesiveto the outer surface 535 of the interconnect structure 525. In suchembodiments, the gel material 605 (if present near corners of theopening 530 at the outer surface 535) may need to be removed beforeattaching the metal cap 610 (e.g., see gel 605 in FIG. 7). The metal capmay be pre-stamped and placed on the device structure 100 (or as apre-stamped sheet placed over all device structures 100 of areconstituted wafer). In other embodiments, cap 610 is a B-stage epoxysheet that is attached to the outer surface 535 of the interconnectstructure 525 and then cured (e.g., by heat or ultraviolet lightradiation). The epoxy sheet may be a pre-cutout sheet and placed on thedevice structure 100 (or as a pre-cutout sheet placed over all devicestructures 100 of a reconstituted wafer). In some embodiments, the cap610 has a height of approximately 0.3 mm.

In embodiments where the device structure 100 is part of a reconstitutedwafer, the device structures 100 are then singulated into separatepackaged pressure sensor devices. In some embodiments, the interconnectstructure 525 as shown has a thickness or height 620 of approximately 40microns (or 0.04 mm), although the height 620 would increase asadditional layers were implemented (e.g., a height of approximately 20microns for each dielectric layer). The height of the p-cell 115 may beapproximately 0.4 mm in some embodiments. The combined height 625 of theresulting packaged pressure sensor device shown in FIG. 6 may beapproximately 1 mm in some embodiments. These dimensions may be of othervalues in other embodiments.

FIG. 7 illustrates a cross-sectional view of an example packagedpressure sensor device attached to a printed circuit board (PCB) 705. Itis noted that the packaged pressure sensor device is shown in a flippedorientation (as compared to FIG. 6) with pressure sensing surface 630 atthe top of the figure and external connection surface 305 at the bottomof the figure. In the embodiment shown, solder bumps or solder balls 710are used to attach and electrically connect the exposed surfaces 310 ofsolder balls 155 to landing pads on the PCB in a ball grid array (BGA)configuration. In other embodiments, the exposed surfaces 310 located onback surface 305 may be mounted to the PCB in a land grid array (LGA)configuration with solder paste, although other connectionconfigurations may be implemented in other embodiments.

External connections are implemented from pads 125 of P-cell 115, ICcomponent 130, and G-cell 135, through interconnects of the interconnectstructure 525, and through respective conductive conduits 145 to solderballs 155. In some embodiments, the solder bumps 710 may add 0.3 mm tothe height of the device, still resulting in a low profile packageddevice. PCB 705 may include electrically conductive features on anon-conductive substrate, which may be a flexible type PCB usingpolyimide or a rigid type PCB using FR4 or BT resin.

FIG. 8 shows a perspective view of an example layout of componentsincluded in the packaged pressure sensor device. In some embodiments,the layout is implemented in a 9 mm by 9 mm layout, although other sizedlayouts may be used in other embodiments. In the embodiment shown,signal connection structure 140 having attached solder balls 155surrounds P-cell 115, G-cell 135, and IC component 130 around theperiphery or edge of the layout. The orientation of the components shownin FIG. 8 (e.g., face-down orientation) is similar to the orientation ofthe components shown in FIG. 1. In some embodiments, IC component 130may be implemented as multiple components (e.g., a microcontroller, anRF block, a power source). In other embodiments, additional componentsmay be included in the layout (e.g., a temperature sensor cell).

FIG. 9 shows a perspective view of a resulting packaged pressure sensordevice fabricated from the layout of components shown in FIG. 8. Theback surface 305 of mold compound 205 is shown facing upwards, with aplurality of surfaces 310 of solder balls 155 exposed through moldcompound 205 along the periphery or edge of the resulting packagedpressure sensor device. Cap 610 is shown facing downwards.

FIG. 10 shows another perspective view of the packaged pressure sensordevice with the back surface 305 of mold compound facing downwards. Cap610 is shown facing upwards, with vent hole 615 providing access to thediaphragm 120 of the p-cell 115.

It is noted that in some embodiments, a p-cell in the presentlydisclosed packaged pressure sensor device may undergo comparable strainas a p-cell that is conventionally packaged using housing filled withgel, over a range of temperatures from −40 C. to 150 C. While bothpackages experience a stress-free region over the diaphragm at 150 C.,both p-cells also experience higher stress as temperature decreases downto −40 C. For example, in some embodiments, at −40 C., the presentlydisclosed packaged pressure sensor device experiences maximum stress atthe corners of the vent hole of the cap. However, with some embodiments,the region above the p-cell's diaphragm in the presently disclosedpackaged pressure sensor device remains in range of strain comparable tothat experienced by the p-cell's diaphragm in a conventional package.The maximum stress experienced by the presently disclosed packagepressure sensor device may also be reduced by using epoxy material asthe cap, which has a comparable CTE (coefficient of thermal expansion)as the underlying mold compound of the package.

By now it should be appreciated that there has been provided a packagedpressure sensor device and method of making that uses an interconnectstructure (or RDL structure) formed over the front side of a pressuressensor die (or cell) and another electronic component, such as anintegrated circuit (IC) component that implements a radio frequency (RF)transmitter, signal processing circuitry, or both. An opening is formedthrough the interconnect structure, which is generally aligned with adiaphragm on the front side of the pressure sensor die or cell, and isfilled with gel. A cap may be placed over the RDL structure, with a venthole generally aligned with the diaphragm, forming a front major surfacefor pressure sensing. The packaged pressure sensor device may alsoinclude backside external connections (which may include solder balls)located on a back major surface of the packaged pressure sensor devicethat is opposite the front major surface.

In an embodiment of the present disclosure, a packaged electronic deviceis provided, which includes: a pressure sensor die having a diaphragm ona front side; an encapsulant material that encapsulates the pressuresensor die, wherein the front side of the pressure sensor die is exposedat a first major surface of the encapsulant material; an interconnectstructure formed over the front side of the pressure sensor die and thefirst major surface of the encapsulant material, wherein an openingthrough the interconnect structure is generally aligned to thediaphragm; and a cap attached to an outer dielectric layer of theinterconnect structure, the cap having a vent hole generally alignedwith the opening through the interconnect structure.

One aspect of the above embodiment provides that the cap includes ametal lid.

Another aspect of the above embodiment provides that the cap includes acured epoxy sheet.

Another aspect of the above embodiment provides that the packagedelectronic device further includes: a gel present within the opening ofthe interconnect structure.

Another aspect of the above embodiment provides that a distance from thediaphragm to the cavity in the cap is less than 50 microns.

Another aspect of the above embodiment provides that the packagedelectronic device further includes: a backside signal connection havinga first surface exposed at the first major surface of the encapsulantmaterial and connected to the interconnect structure, and a secondsurface exposed at a second major surface of the encapsulant material.

A further aspect of the above embodiment provides that the packagedelectronic device further includes: a plurality of backside signalconnections located around a periphery of the packaged electronicdevice.

A still further aspect of the above embodiment provides that thepackaged electronic device further includes: a plurality of solder bumpsattached to the plurality of backside signal connections.

Another aspect of the above embodiment provides that the pressure sensordie further includes at least one pad exposed at the first major surfaceof the encapsulant material and connected to the interconnect structure.

Another aspect of the above embodiment provides that the packagedelectronic device further includes: an integrated circuit (IC) componentincluding a radio frequency (RF) transmitter, the IC component having atleast one pad exposed at the first major surface of the encapsulantmaterial and communicatively coupled to the pressure sensor die throughthe interconnect structure.

A further aspect of the above embodiment provides that the packagedelectronic device further includes: a gyroscope sensor diecommunicatively coupled to the IC component through the interconnectstructure.

In another embodiment of the present disclosure, a method forfabricating a packaged electronic device is provided, the methodincluding: attaching a front side of a pressure sensor die to a carrier,the pressure sensor die having a diaphragm on the front side;overmolding the pressure sensor die with an encapsulant material to forman embedded pressure sensor die, wherein the front side of the pressuresensor die is exposed at a first major surface of the encapsulantmaterial; removing the embedded pressure sensor die from the carrier;forming an interconnect structure over the front side of the pressuresensor die and the first major surface of the encapsulant material,wherein an opening through the interconnect structure is generallyaligned to the diaphragm; and attaching a cap to an outer dielectriclayer of the interconnect structure, the cap having a vent holegenerally aligned with the opening through the interconnect structure.

One aspect of the above embodiment provides that the cap includes ametal lid.

Another aspect of the above embodiment provides that the cap includes aB-stage epoxy sheet; and the method further includes: curing the B-stageepoxy sheet after attaching the B-stage epoxy sheet to the outerdielectric layer.

Another aspect of the above embodiment provides that the method furtherincludes: spinning a gel into the opening through the interconnectstructure and curing the gel, before to attaching the cap.

Another aspect of the above embodiment provides that the method furtherincludes: attaching a backside signal connection structure to thecarrier, wherein a first surface of the backside signal connectionstructure is exposed at the first major surface of the encapsulantmaterial after the overmolding.

A further aspect of the above embodiment provides that the forming theinterconnect structure includes forming a connection to the firstsurface of the backside signal connection structure.

Another further aspect of the above embodiment provides that the methodfurther includes: backgrinding the encapsulant material to form a secondmajor surface of the encapsulant material before removing the embeddedpressure sensor die from the carrier, wherein a second surface of thebackside signal connection structure is exposed at the second majorsurface of the encapsulant material.

Another aspect of the above embodiment provides that the pressure sensordie further includes at least one pad exposed at the first major surfaceof the encapsulant material, and the forming the interconnect structureincludes forming a connection to the at least one pad of the pressuresensor die.

Another aspect of the above embodiment provides that the method furtherincludes: prior to the overmolding, attaching to the carrier one or moreof: an integrated circuit (IC) component including a radio frequency(RF) transmitter, and a gyroscope sensor die, wherein the forming theinterconnect structure includes forming a connection between thepressure sensor die and the one or more of the IC component and thegyroscope sensor die.

Because the apparatus implementing the present invention is, for themost part, composed of electronic components and circuits known to thoseskilled in the art, circuit details will not be explained in any greaterextent than that considered necessary as illustrated above, for theunderstanding and appreciation of the underlying concepts of the presentinvention and in order not to obfuscate or distract from the teachingsof the present invention.

Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under”and the like in the description and in the claims, if any, are used fordescriptive purposes and not necessarily for describing permanentrelative positions. It is understood that the terms so used areinterchangeable under appropriate circumstances such that theembodiments of the invention described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

As used herein, the terms “substantial” and “substantially” meansufficient to achieve the stated purpose or value in a practical manner,taking into account any minor imperfections or deviations, if any, thatarise from usual and expected process abnormalities that may occurduring wafer fabrication, which are not significant for the statedpurpose or value. Also as used herein, the terms “approximately” and“about” mean a value close to or within an acceptable range of anindicated value, amount, or quality, which also includes the exactindicated value itself.

Although the invention is described herein with reference to specificembodiments, various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. For example, additional or fewer components may beimplemented in the device structure 100 of FIG. 1. Accordingly, thespecification and figures are to be regarded in an illustrative ratherthan a restrictive sense, and all such modifications are intended to beincluded within the scope of the present invention. Any benefits,advantages, or solutions to problems that are described herein withregard to specific embodiments are not intended to be construed as acritical, required, or essential feature or element of any or all theclaims.

Furthermore, the terms “a” or “an,” as used herein, are defined as oneor more than one. Also, the use of introductory phrases such as “atleast one” and “one or more” in the claims should not be construed toimply that the introduction of another claim element by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim element to inventions containing only one such element,even when the same claim includes the introductory phrases “one or more”or “at least one” and indefinite articles such as “a” or “an.” The sameholds true for the use of definite articles.

Unless stated otherwise, terms such as “first” and “second” are used toarbitrarily distinguish between the elements such terms describe. Thus,these terms are not necessarily intended to indicate temporal or otherprioritization of such elements.

What is claimed is:
 1. A method for fabricating a packaged electronicdevice, the method comprising: attaching a front side of a pressuresensor die to a carrier, the pressure sensor die having a diaphragm onthe front side; overmolding the pressure sensor die with an encapsulantmaterial to form an embedded pressure sensor die, wherein the front sideof the pressure sensor die is exposed at a first major surface of theencapsulant material; removing the embedded pressure sensor die from thecarrier; forming an interconnect structure over the front side of thepressure sensor die and the first major surface of the encapsulantmaterial, wherein an opening through the interconnect structure isgenerally aligned to the diaphragm; and attaching a cap directly to anouter dielectric layer of the interconnect structure, the cap being anintegral structure having a vent hole generally aligned with the openingthrough the interconnect structure, wherein the cap, except for the venthole, covers an entirety of the outer dielectric layer of theinterconnect structure.
 2. The method of claim 1, wherein the capcomprises a metal lid.
 3. The method of claim 1, wherein the capcomprises a B-stage epoxy sheet; and the method further comprises:curing the B-stage epoxy sheet after attaching the B-stage epoxy sheetto the outer dielectric layer.
 4. The method of claim 1, furthercomprising: spinning a gel into the opening through the interconnectstructure and curing the gel, before to attaching the cap.
 5. The methodof claim 1, further comprising: attaching a backside signal connectionstructure to the carrier, wherein a first surface of the backside signalconnection structure is exposed at the first major surface of theencapsulant material after the overmolding.
 6. The method of claim 5,wherein the forming the interconnect structure comprises forming aconnection to the first surface of the backside signal connectionstructure.
 7. The method of claim 5, further comprising: backgrindingthe encapsulant material to form a second major surface of theencapsulant material before removing the embedded pressure sensor diefrom the carrier, wherein a second surface of the backside signalconnection structure is exposed at the second major surface of theencapsulant material.
 8. The method of claim 1, wherein the pressuresensor die further comprises at least one pad exposed at the first majorsurface of the encapsulant material, and the forming the interconnectstructure comprises forming a connection to the at least one pad of thepressure sensor die.
 9. The method of claim 1, further comprising: priorto the overmolding, attaching to the carrier one or more of: anintegrated circuit (IC) component comprising a radio frequency (RF)transmitter, and a gyroscope sensor die, wherein the forming theinterconnect structure comprises forming a connection between thepressure sensor die and the one or more of the IC component and thegyroscope sensor die.
 10. The method of claim 1, wherein the openingthrough the interconnect structure has sloped walls formed with theencapsulant material with a narrowest portion of the opening beingclosest to the diaphragm on the front side of the pressure sensor die.